Since the initial cloning of Aequorea victoria green fluorescent protein (avGFP) over 20 years ago, fluorescent proteins have become staples of biological imaging. After an initial flurry of activity leading to the development of avGFP variants in the blue to yellow-green wavelength range [1], the bulk of subsequent fluorescent protein research has focused on expanding the fluorescent protein color palette into the red region and improving the brightness and performance of these longer-wavelength variants [2], along with more recent improvements to cyan variants of avGFP (CFPs) [3,4]. Since green and yellow variants of the original avGFP (GFPs and YFPs) perform reliably for many applications, not much effort has been placed on developing novel fluorescent proteins in the green region of the spectrum. However, there is still room for improvement of green and yellow fluorescent proteins, both for routine imaging as well as more advanced applications such as Förster resonance energy transfer (FRET) [5].